The present invention relates to a hand mechanism for a robot, which is attached to the distal end of an arm unit of a robot, comprising independent modules for executing predetermined elementary motions, which modules can be combined with each other, and appropriately combines arbitrary ones of these modules to realize desired elementary motions.
Conventionally, a hand mechanism for a robot, which is interposed between a finger unit and an arm unit of a robot, and causes the finger unit to perform a predetermined posture conversion operation, normally employs an arrangement for causing the finger unit to perform the posture conversion operation in an arbitrary combination state of elementary motions, i.e., a reverse operation, a shift operation, a turn operation, a cushion operation, and a compliance operation.
However, in such a conventional hand mechanism, one hand mechanism employs an arrangement for causing the finger unit to perform a specific posture conversion operation. When the finger unit is required to perform another posture conversion operation, the hand mechanism must be designed in correspondence with the required operation, and must be entirely replaced.
More specifically, assume that a pin is to be inserted in a hole. In this case, although the arrangement of the finger unit remains the same, the arrangement of the hand mechanism must be uniquely designed and manufactured depending on whether this hole is formed in a horizontal surface or an inclined surface.
in this manner, the conventional hand mechanism must be re-designed in correspondence with a change in posture conversion operation of the finger unit, and must be manufactured to have an arrangement unique to the posture conversion operation. For this reason, in order to change the posture conversion operation, a problem of, e.g., long re-design time is pointed out, and a problem of cost is also posed since a common hand mechanism cannot be used for the respective posture conversion operations.
As techniques for solving these problems, Japanese Patent Application Nos. 1-131402 and 1-131403 as the prior applications by the present applicant are known. A hand mechanism disclosed in these prior applications has the following characteristic feature. That is, the hand mechanism is interposed between a finger unit and an arm unit of a robot, and causes the finger unit to perform a predetermined posture conversion operation. The hand mechanism comprises independent modules for executing elementary motions such as a reverse operation, a shift operation, a turn operation, a cushion operation, and a compliance operation, which modules can be combined with each other, and combines arbitrary ones of these modules to cause the finger unit to perform a predetermined posture conversion operation.
In the hand mechanism according to the prior applications, attaching holes separated at a predetermined pitch are formed in the attaching surfaces of each module, the hand unit, and the finger unit, and a position regulation means for attaching the modules in a predetermined attaching state is arranged.
Since the hand mechanism for a robot with the above-mentioned arrangement comprises the independent modules for executing elementary motions such as a reverse operation, a shift operation, a turn operation, a cushion operation, and a compliance operation, which modules can be combined with each other, modules corresponding to elementary motions necessary for a posture conversion operation of the finger unit need only be combined to achieve a predetermined posture conversion operation of the finger unit without redesigning the hand mechanism.
In the hand mechanism according to the prior applications with the above-mentioned arrangement, since a plurality of modules are combined, the dimensional errors, weights, and heights of the modules are accumulated. As a result, when the modules are combined to satisfy a predetermined function, the weight, height, attaching precision, or the like exceeds an allowance, and the hand mechanism cannot often be practically used.
For this reason, in the hand mechanism constituted by combining a plurality of modules, each module is required to have a lightweight, high-precision, and compact structure.
In the hand mechanism according to the prior applications with the above-mentioned arrangement, since a plurality of modules are combined, if the modules are not precisely aligned, the axis of a work undesirably varies upon a rotating operation such as a turn operation or a reverse operation, and the work cannot be placed at an accurate position, thus disabling an assembling operation in practice.